Complexes soufrés du Mercure (II) et du Plomb (II) pour l’optique non linéaire

Date du colloque : 02/2011</p

A chondroitin sulfate small molecule that stimulates neuronal growth

Chondroitin sulfate glycosaminoglycans are sulfated polysaccharides involved in cell division, neuronal development, and spinal cord injury. Here, we report the synthesis and identification of a chondroitin sulfate tetrasaccharide that stimulates the growth and differentiation of neurons. These studies represent the first, direct investigations into the structure−activity relationships of chondroitin sulfate using homogeneous synthetic molecules and define a tetrasaccharide as a minimal motif required for activity

(TTF)2[TTF(CO2H)2(CO2)2]: a wholly TTF material containing TTF radical cations and TTF derived anions

Electrooxidation of tetrathiafulvalene (TTF) carried out in the presence of (Bu4N)2TTF(CO2H)2(CO2)2 as supporting electrolyte affords wholly TTF organic materials in which TTF cations are associated with TTF(CO2H)2(CO2−)2 as counteranions

Base-catalyzed condensation of cyclopentadiene derivatives. Synthesis of fulvalene analogues: strong proaromatic electron acceptors

A series of proaromatic electron acceptors derived from fulvenes were synthesized from tetrachlorocyclopentadiene and previously unknown 1,4-dicyano- and 1,4-dialkoxycarbonyl-2,3-dimethoxy cyclopentadienes. Two reversible one-electron reductions steps observed for fulvalenes coalesce into one two-electron reduction step upon increasing the length of the conjugating bridge

Estimating geological CO2 storage security to deliver on climate mitigation

Carbon capture and storage (CCS) can help nations meet their Paris CO2 reduction commitments cost-effectively. However, lack of confidence in geologic CO2 storage security remains a barrier to CCS implementation. Here we present a numerical program that calculates CO2 storage security and leakage to the atmosphere over 10,000 years. This combines quantitative estimates of geological subsurface CO2 retention, and of surface CO2 leakage. We calculate that realistically well-regulated storage in regions with moderate well densities has a 50% probability that leakage remains below 0.0008% per year, with over 98% of the injected CO2 retained in the subsurface over 10,000 years. An unrealistic scenario, where CO2 storage is inadequately regulated, estimates that more than 78% will be retained over 10,000 years. Our modelling results suggest that geological storage of CO2 can be a secure climate change mitigation option, but we note that long-term behaviour of CO2 in the subsurface remains a key uncertainty

A novel sub-seabed CO₂ release experiment informing monitoring and impact assessment for geological carbon storage

Carbon capture and storage is a mitigation strategy that can be used to aid the reduction of anthropogenic CO2 emissions. This process aims to capture CO2 from large point-source emitters and transport it to a long-term storage site. For much of Europe, these deep storage sites are anticipated to be sited below the sea bed on continental shelves. A key operational requirement is an understanding of best practice of monitoring for potential leakage and of the environmental impact that could result from a diffusive leak from a storage complex. Here we describe a controlled CO2 release experiment beneath the seabed, which overcomes the limitations of laboratory simulations and natural analogues. The complex processes involved in setting up the experimental facility and ensuring its successful operation are discussed, including site selection, permissions, communications and facility construction. The experimental design and observational strategy are reviewed with respect to scientific outcomes along with lessons learnt in order to facilitate any similar future

Land-use planning as a tool for balancing the scientific and the social in biodiversity and ecosystem services mainstreaming? The case of Durban, South Africa

This paper evaluates the role of land-use planning, especially open space systems, in mainstreaming biodiversity and ecosystem services (BES) at the urban level. Whilst there is increasing interest in BES mainstreaming to balance environmental protection with socio-economic development, there is also concern that BES thinking deflects attention from underlying social justice questions. Through the case study of Durban, South Africa – often held as an exemplar in BES mainstreaming – we argue open space systems can offer a pathway to BES mainstreaming that is both scientifically effective and socially just. Yet what makes this possible in Durban, we argue, is (1) a robust scientific evidence base deployed reflexively and sensitively; (2) a move towards explicit emphasis on providing benefits of BES to the most vulnerable people; and (3) supportive policy frameworks plus the presence of biodiversity managers able to navigate the political as well as scientific landscape

420,000 year assessment of fault leakage rates shows geological carbon storage is secure

Carbon capture and storage (CCS) technology is routinely cited as a cost effective tool for climate change mitigation. CCS can directly reduce industrial CO2 emissions and is essential for the retention of CO2 extracted from the atmosphere. To be effective as a climate change mitigation tool, CO2 must be securely retained for 10,000 years (10 ka) with a leakage rate of below 0.01% per year of the total amount of CO2 injected. Migration of CO2 back to the atmosphere via leakage through geological faults is a potential high impact risk to CO2 storage integrity. Here, we calculate for the first time natural leakage rates from a 420 ka paleo-record of CO2 leakage above a naturally occurring, faulted, CO2 reservoir in Arizona, USA. Surface travertine (CaCO3) deposits provide evidence of vertical CO2 leakage linked to known faults. U-Th dating of travertine deposits shows leakage varies along a single fault and that individual seeps have lifespans of up to 200 ka. Whilst the total volumes of CO2 required to form the travertine deposits are high, time-averaged leakage equates to a linear rate of less than 0.01%/yr. Hence, even this natural geological storage site, which would be deemed to be of too high risk to be selected for engineered geologic storage, is adequate to store CO2 for climate mitigation purposes